The pulvinar and lateral posterior nuclei of the thalamus have been viewed as being involved in secondary visual pathways by which visual information from the tectum and pretectal areas could be conveyed to extra-striate cortex. This hypothesis is supported by neuroanatomical studies, but virtually no information is available regarding the functional contributions of superior collicular (or pretectal) inputs to sensory neurons of the pulvinar-LP complex. The experiments proposed in this application seek to determine the effects of cryogenic blockade of the superior colliculus upon visual and extravisual response properties of neurons in the pulvinar-LP complex. The reversible nature of the cryogenic technique makes this a particularly powerful method for investigating this problem. The successful completion of this research would increase considerably our understanding of extrageniculo-striate mechanisms of vision.